In enzymology, an ethanolamine oxidase (EC 1.4.3.8) is an enzyme that catalyzes the chemical reaction

ethanolamine + H₂O + O₂ ${\displaystyle \rightleftharpoons }$ glycolaldehyde + NH₃ + H₂O₂

The 3 substrates of this enzyme are ethanolamine, H₂O, and O₂, whereas its 3 products are glycolaldehyde, NH₃, and H₂O₂.

This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-NH2 group of donors with oxygen as acceptor. The systematic name of this enzyme class is ethanolamine:oxygen oxidoreductase (deaminating). It has 2 cofactors: cobalt, and Cobamide.